Therapeutic drug monitoring of program death-1 (PD-1) inhibitor Serplulimab in cancer patients is of clinical importance in predicting treatment efficacy and assessing adverse reactions. However, the traditional liquid chromatography tandem mass spectrometry (LC-MS/MS) and enzyme-linked immunosorbent assay (ELISA) for antibody drug monitoring are time-consuming and laborious. Herein, a quantum dot nanobeads-based lateral flow immunoassay (LFIA) is developed for rapid and accurate monitoring of the PD-1 antibody drug in 15 min. Both competitive and indirect immunoassays were investigated for PD-1 antibody drug monitoring, and the competitive assay demonstrated better sensitivity and precision. The optimized competitive LFIA had a detection of limit of 5.1 μg/mL; a linear range of 10-100 μg/mL; recovery rates of 99.2%-113.9% at the spiked concentration of 25, 50 and 100 μg/mL; and coefficients of variations (CVs, n = 10) less than 14.5% at 50 μg/mL. The assay has a negligible nonspecific reaction with the interferents of other monoclonal antibody drugs, autoantibodies, hyper lipids, hemolysis, jaundice, and whole blood samples. Method comparison with ELISA in 30 human plasma samples has a good correlation factor of r = 0.87. All in all, the developed quantum dot nanobead-based LFIA system for PD-1 antibody drug monitoring is a versatile tool for rapidly personalized drug therapy at the point of care.